Long-term outcome of 444 patients with distant metastases from papillary and follicular thyroid carcinoma: Benefits and limits of radioiodine therapy

Aim: The goal of this study was to estimate the cumulative activity of I-131 to be administered to patients with distant metastases from thyroid carcinoma. Methods: A total of 444 patients were treated from 1953-1994 for distant metastases from papillary and follicular thyroid carcinoma: 223 had lung metastases only, 115 had bone metastases only, 82 had both lung and bone metastases, and 24 had metastases at other sites. Treatment consisted of the administration of 3.7 GBq (100 mCi) I-131 after withdrawal of thyroid hormone treatment, every 3-9 months during the first 2 yr and then once a year until the disappearance of any metastatic uptake. Thyroxine treatment was given at suppressive doses between I-131 treatment courses. Results: Negative imaging studies ( negative total body I-131 scans and conventional radiographs) were attained in 43% of the 295 patients with I-131 uptake; more frequently in those who were younger, had well-differentiated tumors, and had a limited extent of disease. Most negative studies (96%) were obtained after the administration of 3.7-22 GBq (100-600 mCi). Almost half of negative studies were obtained more than 5 yr after the initiation of the treatment of metastases. Among patients who achieved a negative study, only 7% experienced a subsequent tumor recurrence. Overall survival at 10 yr after initiation of I-131 treatment was 92% in patients who achieved a negative study and 19% in those who did not. Conclusion: I-131 treatment is highly effective in younger patients with I-131 uptake and with small metastases. They should be treated until the disappearance of any uptake or until a cumulative activity of 22 GBq has been administered. In the other patients, other treatment modalities should be used when tumor progression has been documented.